1. Field of the Invention
The present invention relates to a rotor for a turbomachine having blades which can be fitted into slots, wherein the slots are made at an angle to an axis of rotation of the rotor. The invention also relates to a blade for a rotor.
In rotors of turbomachines, high centrifugal forces may occur due to the rotation. In the case of blades which can be fitted in a rotor, there is also the difficulty of constructing the rotor in such a way that it on one hand has adequate strength but on the other hand does not exceed certain dimensional limits, which depend on the loads imposed on the turbomachine. The blades which can be fitted into slots must have a suitable blade root for that purpose. Depending on the structural principle of the connection between blade root and rotor, different stresses occur between the same. Those stresses are distributed in a varying manner over the blade root. One parameter influencing the stresses which occur during operation of the turbomachine is, for example, the installation angle of the blade root in the shaft.
UK Patent Application GB 2 237 846 A relates to a gas turbine for an airplane power plant, which describes a reduction in the mass of the rotor to increase safety when operating at maximum speed. That mass reduction is achieved by providing the roots of the turbine blades with two parts which are separated and spaced apart from each other by a continuous slot. Those parts of the blade roots are spaced apart from each other by two partitions which leads to a spreading of the blade roots.
2. Summary of the Invention
It is accordingly an object of the invention to provide a rotor for a turbomachine having blades to be fitted into slots, and a blade for a rotor, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which reduce strength problems occurring during operation of a rotor and which provide a combination of blade root and slot suitable for this purpose.
With the foregoing and other objects in view there is provided, in accordance with the invention, a rotor for a turbomachine, in particular a turbocompressor, comprising an axis of rotation, slots formed at an angle to the axis of rotation, the slots having different regions of rigidity; and blades having blade roots to be fitted into the slots, at least one of the blade roots having at least two regions of different rigidity adapted and preferably matched to the different regions of rigidity of the slot.
In accordance with another feature of the invention, a correspondingly adapted region of the blade root and a more rigid region, in comparison thereto, of the slot bear against one another or are located opposite one another. This achieves the effect of causing corresponding rigidity values of the slot and the blade root to correspond to one another in such a way that the stresses occurring are evened out overall. In particular, the flow of force during the transmission of force from the blade root into the slot can be rendered favorable given appropriate adaptation.
In accordance with a further feature of the invention, a region of reduced rigidity of the blade root bears against a slot region of maximum stress, in general especially in a region of acute corners of the slot in the rotor, so that no stresses which lead to destruction or material fatigue during prolonged operation of the turbomachine occur during operation of the turbomachine.
In accordance with an added feature of the invention, loads at the slot and loads at the at least one blade root are matched in accordance with forces prevailing in a mainly used turbomachine operating range.
With the objects of the invention in view, there is also provided a blade for a rotor of a turbomachine, comprising a blade root having a form adapted to a slot geometry of slots formed in the rotor, the blade root having two mutually oppositely disposed end surfaces and a rigidity reducing material reduction, preferably at least one recess, in the vicinity of the end surfaces.
In accordance with a concomitant feature of the invention, the blade root has an interior, and the at least one recess, preferably a bore or a milled-out portion, runs from one of the end surfaces into the interior of the blade root.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a rotor for a turbomachine having blades to be fitted into slots, and a blade for a rotor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.